1. Technical Field
Aspects of the present invention relate to an automatic document feeder capable of automatically feeding a document into a reading unit of an image reading device, and an image reading device employing such an automatic document feeder.
2. Related Art
In general, in order to read an image (including text) formed on each of front and back sides of a document (hereafter, referred to as double-sided reading), it is necessary to reverse a carrying direction of the document after finishing reading of the front side of the document by a reading unit, and to read the back side of the document being carried in the reversed carrying direction by carrying the document to the image reading unit.
For example, If the document having a plurality of sheets of paper stacked in a vertical direction on a document tray is to be read from a sheet of paper placed at the bottom one-by-one to perform double-sided reading, when the sheets of paper for which reading are finished are simply placed on a output tray in sequence, the sheets of paper for which reading is finished are stacked on the output tray such that the first sheet of paper for which reading is finished first is placed at the bottom on the paper output tray. Therefore, in this case, the page sequence of the sheets of paper placed on the document tray is different from the page sequence of the sheets of paper placed on the output tray.
For example, assuming that two sheets of paper A and B (documents A and B) are placed on the document tray such that the front side of the document A, the back side of the document A, the front side of the document B and the back side of the document B are defined as the first, second, third and fourth pages, respectively, and that the document A is stacked on the document B are stacked while facing the front side of each document upward, the two documents A and B are output to the output tray in a state where the document B is placed on the document A and the front side of each document faces upward.
For this reason, the documents which have been arranged on the document tray in the order of the first, the second, the third and the fourth pages are arranged, on the output tray, in the order of the third, the fourth, the first, and the second pages. Thus, the page sequence of the documents placed on the document tray becomes different from the page sequence of the documents on the output tray.
On the other hand, in order to read an image only from the front side of the document (hereafter, referred to as single-side reading), the automatic document feeder may outputs the document for which the reading is finished to the output tray without reversing the carrying direction of the document. Therefore, the page sequence of the documents on the document tray does not become different from the page sequence of the documents on the output tray.
Japanese Patent Provisional Publication No. HEI 11-314856 (hereafter, referred to as JP HEI 11-314856A) discloses an automatic document feeder configured such that a first output tray dedicated for the single-side reading is located on one side with respect to a reading unit and a second output tray dedicated for the double sided reading is located on the other side with respect to the reading unit so that the page sequence of the document on a document tray does not become different from the page sequence of the document on the output tray when the double-sided reading is performed.